CVE-2021-21273

Exploitation

Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.

SSVC decision

Not assessed by CISA

EPSS probability

1.80% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 78.3% of scored records. A rank, not a probability.

NVD base score

6.1 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

NVD analysis status

Modified. NVD last modified this record on 2026-06-17.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2021-02-26 17:25Z5 YR AGO

Last updated

2024-08-03 18:09Z2 YR AGO

Reserved

2020-12-22

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

Low (CVSS 3.1)

CNA CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

Weaknesses

• CWE-601URL Redirection to Untrusted Site ('Open Redirect')Base

Data version

5.1

Document digest

ce3e55085d5f89cc6abb8eb398360ba6ff2a9c18dd85a834c425b983465795dc

• github.comhttps://github.com/matrix-org/synapse/releases/tag/v1.25.0x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/security/advisories/GHSA-v936-j8gp-9q3px_refsource_CONFIRM
• github.comhttps://github.com/matrix-org/synapse/pull/8821x_refsource_MISC
• github.comhttps://github.com/matrix-org/synapse/commit/30fba6210834a4ecd91badf0c8f3eb278b72e746x_refsource_MISC
• lists.fedoraproject.orgFEDORA-2021-a627cfd31ehttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/vendor-advisoryx_refsource_FEDORA